The present invention relates to the apparatus and method for illuminating optical fibers.
Optical fibers are known to the art in several forms. These include drawn and treated glass and various plastic fibers, any of which may additionally be clad or coated. These fibers, typically used in long bundles, transmit light from end to end over substantial distances. In the Related Application cited above, the optical fibers additionally provide lateral transmission of light which emerges from the sides of the fibers to provide illumination along the entire length of the fiber.
Many applications, such as those using multiple fibers in a bundle, require a light source or sources capable of providing light to more than one end of the fiber bundle. In the Related Application cited above, illumination is supplied at both ends to provide illumination by means of lateral emission of light along the lengths of the fibers, and it has been determined that illuminating both ends of such optical fibers provides more uniform illumination along the lengths thereof.
Light sources adapted to provide illumination to optical fibers suffer from a number of disadvantages. Many sources of illumination become overheated for applications involving plastic fibers, and where the light source is enclosed within a housing, the housing may become dangerously hot to the touch. In addition, the heat generated by the enclosed light source may damage various components of the lighting system including color filters and the optical fibers themselves.
This danger of overheating has sometimes been overcome by providing forced-air cooling and heat-reflective mirrors. Even with fans, previous designs in the prior art restricted the wattage of light bulbs used within the enclosure, typically, to less than 100 watts in order to avoid damaging the optical fibers and associated optical components. This power limitation is considered a serious disadvantage where high level illumination is required, such as where lateral transmission of light from fibers must be visually perceptible against ambient light levels.
It is desirable in some applications to provide a light-tight source of illumination for optical fibers. However, light-tight enclosures often contribute to the overheating problem since the enclosure usually interferes with the free flow of cooling air.
Illuminating more than one end of a bundle of optical fibers may be accomplished with a separate illumination source at each end with the ends of the bundled fibers presented to a focused light source. However, where fibers are simply bundled together, it may be difficult to attain regular and easily reproducible results since the bundling may vary from one installation to the next. Also, it is more difficult to radiate away accumulated heat where the fibers are bundled, thus leading to an increased likelihood of heat-related damage to the fibers.